Elevator equipment usually comprises an elevator car and at least one counterweight, which are moved in opposite sense in an elevator shaft. The elevator car and the at least one counterweight in this regard run in or along guide rails. For reasons of safety, elevator equipment is usually equipped with a safety brake device which is part of a safety device. The safety brake device engages the guide rails of the elevator car and/or of the counterweight. The speed of movement of the elevator car or of the counterweight is thereby slowed down or reduced to zero by fixing of the safety brake device to the guide rail. Triggering of the brake or fixing is carried out by means of a speed limiter device which constantly monitors and limits the speed of the elevator car or of the counterweight.
This limitation of the speed is carried out, for example as disclosed in patent specification EP-B1-1 298 083, by coupling the elevator car or the counterweight with a limiter cable of the speed limiter by means of a linkage and lever mechanism. The limiter cable is guided in the shaft head over a cable pulley of the speed limiter and in the shaft pit over a return roller. During travel, the elevator car drives the limiter cable and the speed of the elevator car is monitored by the speed limiter via the limiter cable. In the case of excess speed of the elevator car the speed limiter blocks the cable pulley, in which case the elevator car drags the limiter cable over the cable pulley. By the friction at the cable pulley the limiter cable actuates the lever mechanism at the elevator car and engages the safety brake device in that the limiter cable exerts, by way of the linkage and lever mechanism, a tension on the safety brake device arranged at the elevator car. This tension in turn brings one or also two wedge-shaped and roller-mounted brake shoes of the safety brake device into a first (frictional) contact setting at the guide rail. A spring column, which is formed from plate springs and which is arranged opposite the brake shoes in a pincer-like double-lever construction, is thereby in turn activated. It is thus achieved that the tension force in the linkage and lever mechanism is not the actual braking force, but only the triggering force for the safety brake device. The effective braking force is exerted by, in particular, the spring column. The same way of functioning applies to the counterweight. Monitoring of the car speed can also be carried out, for example, electronically and the safety brake device triggered, for example, electromagnetically. The traditional mechanical speed limiter and the traditional limiter cable are redundant in this last-mentioned variant.
Patent specification U.S. Pat. No. 2,581,297 discloses a safety device with a similarly constructed safety brake device, in which the braking force is generated by a spiral spring.
However, these known safety brake devices have the following disadvantages:                The force store element, be it a spring column formed from individual plate springs as in EP-B1-1 209 083 or a helical spring as in U.S. Pat. No. 2,581,297, has no safety reserves.        Failure of this single force store element has the consequence of failure of the safety brake device.        There are countries having safety regulations for safety-relevant parts in elevator equipment which prescribe a safety reserve which would not be fulfilled by the two known safety brake devices.        The manner of functioning of the safety brake device can be optimized with respect to preservation of material, the course of the braking force and thus the deceleration sensed by elevator users in the elevator car.        